/*
 * 上海远境文化传媒有限公司 版权所有
 */
package ext.jpa.snowflake;

import cache.uuid.Base58;
import helper.LocalIpAddressHelper;
import org.apache.commons.lang3.RandomUtils;
import play.Logger;

import java.net.InetAddress;
import java.util.List;

/**
 * Snowflake ID生成.
 */
public class SnowflakeUtil {

    private static SnowflakeUtil instance;

    static {
        long node = System.currentTimeMillis() % 32L;
        Logger.info("LOG02923: SnowflakeUtil node = " + node);
        List<InetAddress> ipAddresses = LocalIpAddressHelper.getSortedPrivateIp();
        long centerid = 0L;
        if (ipAddresses.size() > 0) {
            byte[] address = ipAddresses.get(0).getAddress();
            centerid = ((long) address[address.length - 1]) % 32L;
            Logger.info("LOG02943: centerid = " + centerid);
        } else {
            centerid = RandomUtils.nextLong() % 32L;
        }

        instance = new SnowflakeUtil(node, centerid);
    }

    public static long nextLong() {
        return instance.nextId();
    }

    public static String nextBase58() {
        byte[] byValue = new byte[8];
        long value = nextLong();
        long2bytes(value, byValue, 0);
        String shortUuid = Base58.encode(byValue);
        return shortUuid;
    }

    protected static void long2bytes(long value, byte[] bytes, int offset) {
        for (int i = 7; i > -1; i--) {
            bytes[offset++] = (byte) ((value >> 8 * i) & 0xFF);
        }
    }

    private long workerId;
    private long datacenterId;
    private long sequence = 0L;

    private long twepoch = 1497701008932L;

    private long workerIdBits     = 5L;
    private long datacenterIdBits = 5L;
    private long maxWorkerId      = -1L ^ (-1L << workerIdBits);
    private long maxDatacenterId  = -1L ^ (-1L << datacenterIdBits);
    private long sequenceBits     = 12L;

    private long workerIdShift      = sequenceBits;
    private long datacenterIdShift  = sequenceBits + workerIdBits;
    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private long sequenceMask       = -1L ^ (-1L << sequenceBits);

    private long lastTimestamp = -1L;

    public SnowflakeUtil(long workerId, long datacenterId) {
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
        Logger.info(String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId));
    }

    public synchronized long nextId() {
        long timestamp = timeGen();

        if (timestamp < lastTimestamp) {
            Logger.error(String.format("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp));
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;

        return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }
}
